Clint Eastwood’s last two films, American Sniper and Sully, delved into ideas of modern-day heroism with a troubled complexity that was easily – sometimes even wilfully – overlooked. Both had haunted undersides, practically functioning as Rorschach tests for how viewers might be willing to conceive of American exceptionalism.

The 15.17 to Paris is ready to be bracketed with them as the third part of an unofficial trilogy, concerning as it does the impromptu heroics of three young Americans on board a Thalys train from Amsterdam in August 2015. A Moroccan gunman opened fire in their carriage, and these three men, along with other passengers, managed to subdue and and disarm him without anyone being killed.

Spencer Stone, Anthony Sadler and Alek Skarlatos received many decorations, including the French Legion of Honour, for the lives they undoubtedly saved, and now they’re granted a kind of victory lap not only in having their story put before the cameras, but even – here’s the curious twist – in filling the three main roles by playing themselves.

The film makes no attempt to pretend these are dudes who can act – that’s not the point – and sometimes it has the feel of a borderline-documentary reconstruction, asking them to revisit not only the pivotal attack, but the entire lead-up of their travels in Europe beforehand.

Their input in the script is intended to make all this preamble as authentic as possible. But the trouble is the feeble dramatic shape Eastwood has given the whole thing: it’s a narrative of almost nothing interesting happening until the moment of crisis in the very last reel. It’s weird to be put in the position of wanting the terrorist attack to hurry up and happen, already, but there’s damnably little else to keep us occupied.

The extended travelogue in the middle is a desert of incident – several scenes revolve entirely about whether they should stay on in Amsterdam an extra night, because the bars are pretty cool, and they keep hearing Paris isn’t all that, and so on. Eastwood, understandably, shoots scenes in Amsterdam nightclubs like an 87-year-old who wants in and out of there without being forced to do Sambuca shots.

The 15:17 to Paris Credit:
Karen Ballard

Unless you count one dubious moment of upskirt ogling, there’s no adrenalin or local colour sparking any of this stuff to life – nothing to be milked except a thin sense of destiny. Still, milk it we do: “Do you ever feel like your life is catapulting towards some greater purpose?”, two of the guys ask each other, in a baldly scripted, they-definitely-didn’t-say-that moment, on a Venice rooftop.

Still, Eastwood’s attempts to establish these characters a decade earlier as schoolboys are even more vacuous. And this – the prologue – is the section of the film with recognisable actors. Judy Greer and Jenna Fischer play tough-cookie religious moms whose first scene is a badly written beef with a teacher. Thomas Lennon is the school principal. And the child performances Eastwood gets are so off-key, they have the weird effect of making the real-life Stone, Sadler and Skarlatos look like absolute pros, comparatively speaking. Even the notorious fake baby in American Sniper may deserve a fresh appraisal.

Without his military training, it’s unlikely that Stone would have known what to do with the fellow passenger bleeding out at his feet when it came to the crunch. And without a defect in his vision, he might have enrolled successfully in the US Air Force and not been discharged before going into active service. We tick off these earlier beats in his life, because there’s not much else to do except absorb that he’s a decent, regular guy. Nothing here feels probing or subversive so much as numbingly on-message.

It’s workaday hagiography about have-a-go heroes, respectful of their lives and efforts, but artistically hardly bothering. For all that they lack acting ability – and playing yourself is actually the toughest of performance tasks, not the easiest – there’s no way this trio should be held culpable for how banal the film winds up feeling.

They pulled off a gruelling, life-or-death struggle with their assailant, one Ayoub El-Khazzani. But it’s a losing battle against this script.